At DoubleBitcoin you don't have to make contracts or pledge your property. There are no lenders and no debtors. Everything is actualy real simple: one participant asks for help — another one helps. All profits are generated by new investments.

First Step: Choose the amount to double and provide your personal wallet to receive earned profit.
Sencond Step: Deposit any amount (min 0.001 BTC) to the unique generated deposit address.
Third Step:Do Not close deposit window and wait for 3 confirmations, then start receiving profit with no further effort.